A number of methods have been heretofore proposed for the purpose of providing prolonged release of a drug within a living body, particularly at a prescribed internal region. Ideally, the donor is desired to be wholly disintegrated and eliminated after completion of the action of donation. For this purpose, the housing part of the donor should be biodegradable.
A drug release device making use of this principle is disclosed in U.S. Pat. No. 3,911,098, corresponding to Japanese Patent Application (OPI) No. 123815/75 (The term "OPI" as used herein refers to a "published unexamined Japanese patent application".). The method for the manufacture of this drug release device comprises intimately mixing a given drug with a chitin solution and molding the resultant blend in a given shape,to thereby provide a release device. This method, however, is practicable only with a derivative of chitin which is soluble in water. Other chitins and chitin derivatives which are not soluble in water suffer from a disadvantage that since most solvents of chitins are highly reactive, drugs which are bioactive components are often chemically degraded and deactivated. As examples of solvents for chitins, trichloroacetic acid, dichloroacetic acid, N-methyl pyrrolidone, and hexafluoroisopropyl alcohol have been known to the art. To ensure intimate blending of a drug and a chitin, the practice of first dissolving the chitin in a solvent as described above and subsequently dispersing the drug in the resultant solution has been followed. This practice has a disadvantage that during the course of the dispersion, the drug is liable to lose activity and the device consequently obtained is deficient in efficacy.
The inventors have conducted studies with a view to providing a biodegradable drug donor improved so as to overcome the drawbacks suffered by the conventional device as described above. It has consequently been found that a donor formed by wrapping a given drug with a film of chitin protects the drug against loss of activity and enables the drug to be gradually and substantially uniformly released to the living body. Such is described in Japanese Patent Application (OPI) No. 134412/82. However, when this donor makes use of hollow fibers, for example, the method for the manufacture thereof proves to be rather complicated because the drug and the film of chitin are two separate substances, and therefore must be prepared separately from each other and subsequently combined. Therefore, the development of a method which permits a drug donor of such advantageous behavior to be easily produced would be very desirable.